Limit switch



H. E. HODGSON LIMIT SWITCH Aug. 22, 1950 2 Sheets-Sheet 1 Filed Dec. 2, 1946 hm Mmmzw Mewvwzx Aug. 22, 1950 H. E. HODGSON 2,519,907

LIMIT SWITCH Filed Dec. 2, 1946 2 Sheets-Sheet 2 walls of casing I2.

Patented Aug. 22, 1950 LIMIT SWITCH Howard E. Hodgson, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a

corporation of Delaware Application December 2, 1946, Serial No. 713,533

4 Claims.

This invention relates to limit switches and more particularly to gear type limit switches for use in connection with motor driven apparatus such as machine tools, garage doors, small hoists and various other machine applications which require accurate stopping in opposite limits.

The invention has among its objects to provide an improved gear type limit switch which is exceedingly compact and rugged in construction, positive and reliable in operation and readily adjustable to provide for accurate stopping of a controlled device in selected limits.

Another object is to provide a limit switch of the aforesaid type which is completely enclosed and is provided with readily accessible means on the exterior thereof for effecting manual adjustment of either of its stopping limits.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will now be described, it being understood that the embodiment illustrated is susceptible of modification without departing from the spirit and scope of the appended claims.

In the drawing,

Figure l is a side view of a limit switch embodying the invention, with a portion of an enclosing casing therefor broken away and shown in section;

Figs. 2 and 3 are sectional views on lines 2-2 and 33, respectively, of Fig. 1;

Fig. 4 is an end view of the limit switch shown in Fig. 1;

Fig. 5 is a side elevational view of certain parts of the switch operating mechanism illustrated in Figs. 2 and 3, and

Fig. 6 is a schematic View of the gear operating .mechanism illustrated in Fig. 1.

Referring to Fig. 1, the same illustrates a pair of control switches I and 2 and an operating mechanism therefor including a driving pinion 3 and two sets of switch operating gears 45 and 6l, the former set being associated with switch I and being normally connected to driving pinion 3 through the medium of a pair of idler pinions 8 and 9, and the latter set being associated with switch 2 and being normally connected to said driving pinion through the medium of a pair of idler pinions Ill and II. The above parts are housed within an elongated rectangular enclosing casing i2 having a removable top cover it. Driving pinion 3 is fixed to a drive shaft I I which is rotatably supported and held against axial movement within bearings provided in the end The end walls of said casing are also provided with openings for receiving shafts I5 and I5, the former shaft being associated with the two sets of operating gears 4-5 and 6-4, and the latter being associated with the two sets of idler pinions 8-9 and III-II.

More specifically, the control switches I and 2 may be of any desired construction, the switches illustrated each being provided with an insulating base I8 which carries a pair of stationary contacts I9 and a cooperating movable bridging contact 20 having a reciprocable operating element 2| associated therewith. The contacts associated with switches I and 2 are illustrated by dotted lines in Fig. 1 and it is assumed that the operating element 2I of switch I is biased to move downwardly to maintain its associated bridging contact in circuit opening position and that the operating element 2| of switch 2 is biased to move downwardly to maintain its associated bridging contact in circuit closing position. The insulating bases I3 of switches I and 2 are mounted side by side upon the top wall of an inverted L-shaped bracket 22. This bracket has its upper wall secured by screws 23 to ledges 24 formed on the end walls of casing I2, and as shown in Figs. 2 and 3 the operating elements 2| of switches I and 2 extend downwardly through openings in said wall.

The two sets of switch operating gears 4-5 and 6I are rotatably mounted upon their associated shaft I5 and as shown in Fig. 1 said gear sets are spaced apart by a washer 25 which is also rotatably mounted upon said shaft. The opposing faces of gear sets 45 and 6-'| are provided with abutting cam projections 11 of cylindrical form each of which is provided with a peripheral slot 12. The cam projections a of operating gears 4 and 5 cooperate with an operating slide 26 associated with switch I and the cam projections a of gears 6 and I cooperate with an operating slide 2? associated with switch 2. As shown in Fig. 5, the slides 26 and 21 are slidably mounted within vertically disposed slots 28 formed in the side wall of bracket 22 and as shown in Figs. 2 and 3 said slides are located to one side of their associated cam projections a and are provided with cam engaging teeth 29 and 38, respectively. Also as shown in Fig. 5, downward movement of the slides 26 and 21 is stopped by springs 3| which are mounted in the lower ends of slots 28.

As hereinbeiore stated, the switch operating gears i-5 are normally connected to the driving pinion 3 through the medium of a pair of idler pinions 8 and 9 and the switch operating gears 6 and I are normally connected to said driving pinion through the medium of a pair of idler pinions it and il. Each pair of idler pinions 8.l and I iI I is provided with a connecting sleeve portion 33 and said pinions are rotatably mounted upon shaft E6 and are also movable axially thereon. As shown in Figs. 1 and 6, idler pinion 9 is normally held in meshing engagement with the left hand end of driving pinion 3,

projections E and 1*.

, 3 by a spring 34 which is held under compression between idler pinion 8 and the left hand end wall of easing l2, and idler pinion In is normally held in meshing engagement with the right hand end of said driving pinion by a spring 35 which held under compression between idler pinion H and the right hand end wall of casing [2.

The above described gear operating mechanism is so designed that gears 5 and 6 are driven from pinion 3 at a slightly slower speed than are the gears 4 and i. This may be accomplished by providing the several idler pinions 8, 9, l and II with the same number of teeth and by providing gears 4 and l with one less tooth than the gears 5 and 6. For example, gears 4 and 1 may be provided with thirty teeth; and gears 5 and 6 with thirty=one teeth;

The operation of the aforedescrioe'd mechanism will now be more fully set forth. Slide 26 is normally held in the full line position shown in Fig. 2 by engagement of its associated tooth 28 with the circular surfaces of cam projections 4 and 5 to held the operating element 2| of switch 1 in circuit closing position. Assume that drive shaft H is operating in a counterclockwise direction to drive the switch operating gears ,4 and 5 in a corresponding "direction, as indicated by arrows in Fig. 2. Slide 23 will be maintained inits full line position until the slots b in cam projections 4 and 5 are brought into substantial alignment with each other and with the tooth 29. Since gears 11 and 5 are driven at different speeds the slots 12 in cam projections i and 5 will b brought into alignment with each other and with tooth '29 at some point during counter- 1 clockwise rotation of shaft 14-, such point being determined by the setting of said gears with respect to the driving pinion 3'. When this occurs tooth 29 drops into it associated slots 1) and upon continued rotation of gears 4, and Sin a counterclockwise direction slide 3% is moved downwardly by engagement within said slots into the dotted line position shown in Fig. 2 to permit movement of the operating element 21 of switch into circuit opening position. Upon further rotation of gears 4 and in a counterclockwi direction slide 233 is held in the dotted line position shown in Fig. 2 against the action of its associated spring 31 by engagement of tooth 23 with the circular surfaces of cam projections 4 and 5 now-that drive shaft !4 is reversed to rotate gears 4 and 5 in a clockwise direction. The slots b in cam projections 4 nd i will again be brought into substantial alignment with each other and in Fig. 1 for return of the operating cement -2l of switch I to circuit closing position. A is apparent, during clockwise rotation of drive shaft I 4, slide 26 is returned to the full line position shown in Fig. 2 at substantially the same point at which the same was moved out of such position during counterclockwise rotation of said shaft.

The operating slide 2'! associated with switch 2 is normally held against the action of its associated spring 3| in the full line position illustrated in Fig. 3 by engagement of its associated tooth 30 with the circular cam surfaces on cam Upon clockwise rotation of shaft l4 gears 6 and I are driven in a corresponding direction and operating slide 27 is held Assume 4 in its full line position shown in Fig. 3 until the slots b in cam projections E and '1 are brought into substantial alignment with the tooth 30 on slide 21. This occurs "at a point which is determined by the setting of gears 6 and l with respect to driving pinion 3. The tooth 30 on slide 21 then drops into the slots b of cam projections 6 and l and upon continued rotation of gears 6 and l in a clockwise direction slide 21 is moved upwardly into the dotted line position shown in Fig. 3 to maintain the switch operating element 2| of switch 2 in circuit opening position. Upon reversal of shaft M the tooth 3i? reengages within the slots 22 in cam projections 8 and l and slide 21 is returned to the full line position shown in Fig. 3 at substantially the same point 'at which the same was moved out of such position during clockwise rotation of said shaft.

The above described limit switch mechanism is provided with manual adjusting means which will now be described. As shown in Figs. '1 and '6, idler shaft l6 has a key in fixed thereto which is located between the idler pinions 9 and I0 and the opposing faces of said idler pinions are provided with projections 38 and 39, respectively, which are slotted to receive said key. Idler shaft is has an adjusting knob 40 fixed to the left hand end thereof for rotating the same and for also efie'cting axial adjustment thereof. Also shaft 16 is provided with axially spaced grooves '42, 43 and '44 for receiving a releasable latching spring 45 which is fixed to the left hand end wall of casing 12.

Idler shaft 16 is normally held against axial movement in the intermediate position illustrated by full lines in Fig. 6 by engagement of latching spring 45 within the groove 43. With idler shaft ['6 in it's intermediate position key 3'! is located n'iidway between the ends of driving pinion 3 so that idle .pini'ons '9 and 10 are held in meshing engagement with said driving pinion under the action of their associated springs *34 and 35. Upon outward movement of idler shaft ['6 into a position wherein latching spring 45 engages within groove 44, idler pinion 9 i's'in'oved out or meshing engagement with driving pinion 3 by key 31 and said key is disengaged from projection 39 on idler lpinion I0 and engages within the slots in projection 38 on idler pinion 9. Gears '4 and 5 are then ='operatively connected to idler shaft 46 through the medium of their associated idler ;pini'ons 8 and '9 and by rotating knob 40 said gears can be set in any desired angular position with respect to drive shaft '14. Upon inward movement of idler shaft it into a position wherein latching spring 45 engages within recess '42, idier pinion 10 is moved out of engagement with driving pinion 3 by key 31 and said key is disengaged from project'ion 38 on idler .pinio'n 9 and engages Within the slots in projection 39 on idler pinion [0. Gears 6 and "l are then operatively connected to idler sha'ft it through the medium of their esso'o'ia'ted pinions l0 and "ll and said gears can then be set in any desired angular position with respect to *d'riv'e shalft 1' 4 by rotating knob 40.

In setting upthe aforedescribed limit switch mechanism the drive shaft 14 thereof is coupled to 'the device to be "controlled, and said device is theio inoved into one of its limits, as for exainple th'e liinit correspond-ing to switch I. Gears arrow A in 'Fig. 4. Idler shaft F6 is then operated to reconnect gears 4 and 5 to driving pinion 3 and the device to be controlled is moved into its opposite limit. Gears 8 and I are then adjusted by means of idler shaft It so that switch 2 is just about to open when knob it) is rotated in the direction of the arrow B in Fig. 4. Gears 6 and l are then reconnected to driving pinion 3 by restoring idler shaft Hi to its normal intermediate position. As is apparent, switches i and 2 are now set to effect accurate stopping of the driven device in desired opposite limits.

What I claim as new and desire to secure by Letters Patent is:

1. A limit switch mechanism comprising a pair of control switches, a pair of geared cam members associated with each of said. switches, a common drive for said cam members including a driving pinion, and two sets of idler pinions normally held in meshing engagement with said driving pinion to provide for continuous rotation of each pair of cam members by said driving pinion in the same direction but at diiferent relative speeds, each of said switches being movable out of a given normal position by rotation of its associated cam members in one direction and being restored to normal position by rotation of its associated cam members in a reverse direction but only when its associated cam members are brought into substantial alignment and a manual adjusting element associated with said idler pinions for setting said pairs of cam members with respect to said driving pinion to provide for operation of said switches at selected limits, said adjusting element being operable to disengage either of said sets of idler pinions from said driving pinion and to reengage the same therewith and being also operable to effect rotation of either set of idler pinions upon disengagement thereof from said driving pinion for adjustment of the relative angular positions of the cam members associated therewith.

2. A limit switch mechanism comprising a pair of control switches, a pair of geared cam members associated with each of said switches, drive for said cam members including a single driving pinion, and two sets of idler pinions normally held in meshing engagement with said driving pinion to provide for continuous rotation of each pair of cam members by said driving pinion in the same direction but at different relative speeds, each of said switches being movable out of a given normal position by rotation of its associated cam members in one direction and being restored to normal position by rotation of its associated cam members in a reverse direction but only when its associated cam members are brought into substantial alignment and a common supporting shaft for said idler pinions, said supporting shaft being movable axially in opposite direction out of a given normal position into given extreme positions to selectively disconnect said sets of idler pinions from said driving pinion and being also rotatable in said extreme positions to effect rotation of the disengaged set of idler pinions for adjustment of the relative angular positions of the cam members associated therewith.

3. A limit switch comprising an enclosing casing, a switch mechanism mounted within said casing and comprising a pair of control switches, a pair of geared cam members associated with each of said switches, a drive shaft mounted within hearings in said casing and having a driving pinion fixed thereto, two sets of idler pinions associated with said cam members and normally held in meshing engagement with said driving pinion to provide for continuous rotation of each pair of cam members by said driving pinion in the same direction but at diiferent relative speeds, each of said switches being movable out of a given normal position by rotation of its associated cam members in one direction and being restored to normal position by rotation of its associated cam members in a reverse direction but only when its associated cam members are brought into substantial angular alignment and an idler shaft mounted within said casing and associated with said sets of idler pinions to effect setting said pairs of cam members with respect to said driving pinion for operation of said switches at selected limits, said idler shaft being accessible from the exterior of said enclosing casing and being axially movable in opposite directions out of a given normal position into given extreme positions to selectively disconnect said sets of idler pinions from said driving pinion and being also rotatable in said extreme positions to effect rotation of the disengaged set of idler pinions for adjustment of the relative angular positions of the cam members associated therewith.

4. A limit switch mechanism comprising a pair of control switches, a pair of rotatable operating cams associated with each of said switches, driving means for said cams including a common reversible drive shaft, said driving means operating upon rotation of said drive shaft in either direction to rotate each of said pairs of cams in a corresponding direction and at different speeds, and each of said pairs of cams operating when rotated in one direction into corresponding angular positions to open its associated switch and when rotated in an opposite direction out of such corresponding angular positions to close its associated switch, and ad- ,iusting means associated with said driving means for selectively adjusting said pairs of cams with respect to said drive shaft to provide for operation of said switches by said drive shaft at selected limits, said adjusting means including a single manual adjusting part operable to selectively disconnect said pairs of cams from said drive shaft and to reconnect the same thereto, and also operable to effect angular adjustment of either of said pairs of cams with respect to said drive shaft upon disconnection thereof from said shaft.

HOWARD E. HODGSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,097,487 Kinnear Nov. 2, 19137 2,221,324 Goff Nov. 12, 1940 2,348,141 Luhn May 2, 1944 2,389,350 Exner Nov. 20, 1945 2,451,416 Thomas Oct. 12, 1948 FOREIGN PATENTS Number Country Date 196,116 Germany Feb. 27, 1908 

